Push-pull switch having self-biasing elastomeric material contacts with discrete conductive particles dispersed therein

ABSTRACT

A push-pull switch having a pair of axially aligned, extensible and retractable links and a pair of resilient, normally nonconductive switching members one of which may be compressed and rendered conductive in response to extension of the links and the other of which may be compressed and rendered conductive in response to retraction of the links. The resilience of the compressible switching members normally maintains the links in such positions that neither of the switching members is conductive.

United States Patent [191 Du Rocher Mar. 26, 1974 [5 PUSH-PULL SWITCHHAVING 3,629,774 12/1971 Crites 338/114 SELFJHASING ELASTOMERIC MATERIAL2,441,888 5/1948 Lansing..... ZOO/l6 B 3,386,067 5/1968 Costanzo 338/100CONTACTS WITH DISCRETE 2,793,260 5/1957 Ciosek 200/153 w ux CONDUCTIVEPARTICLES DISPERSED 3,258,549 6/1966 SIOl 200/153 v ux THEREIN Inventor:Gideon A. Du Rocher, Mt. Clemens,

Mich.

Essex International Inc., Fort Wayne, Mich.

Filed: Mar. 23, 1972 Appl. No.: 237,297

Related U.S. Application Data Division of Ser. No. 851,343, Aug. 19,1969, Pat. No. 3,653,237.

Assignee:

References Cited UNITED STATES PATENTS 4/1970 Harshman et al 200/159 XPrimary Examiner-Herman J. Hohauser Assistant Examiner-Robert A.Vanderhye Attorney, Agent, or Firm-Learman & McCulloch [5 7] ABSTRACT Apush-pull switch having a pair of axially aligned, extensible andretractable links and a pair of resilient, normally non-conductiveswitching members one of which may be compressed and rendered conductivein response to extension of the links and the other of which may becompressed and rendered conductive in response to retraction of thelinks. The resilience of the compressible switching members normallymaintains the links in such positions that neither of the switchingmembers is conductive.

8 Claims, 3 Drawing Figures VIII/III] PUSH-PULL SWITCH HAVINGSELF-BIASING ELASTOMERIC MATERIAL CONTACTS WITH DISCRETE CONDUCTIVEPARTICLES DISPERSED THEREIN RELATED APPLICATION This application is adivision of application Ser. No. 851,343, filed Aug. 19, 1969, now US.Pat. No. 3,653,237.

The invention disclosed herewith relates to a switch construction of thepull-push type for operating electrical devices such as reversible DC.motors and includes a pair of compressible, resilient, normallynonconductive switching members. The switching members are so arrangedwith relation to the remaining switch structure that one of them iscompressed and rendered conductive when the switch structure issubjected to a pulling force and the other of the switching members iscompressed and rendered conductive when the switch structure issubjected to a pushing force. The arrangement is such that it is notpossible to render both switching members conductive simultaneously.

A switch of the kind disclosed herein is particularly well adapted forcontrolling power apparatus for locking and unlocking the door latchingmeans of vehicles, but has many other uses.

An object of this invention is to provide an improved switchconstruction for controlling the operation of power apparatus such asreversible electric motors.

Another object of the invention is to provide a switch construction ofthe kind referred to which precludes energization of a reversible motoror the like in more than one direction at any one time.

Other objects and advantages of the invention will be pointed outspecifically or will become apparent from the following description whenit is considered in conjunction with the appended claims and theaccompanying drawings, wherein:

F l6. 1 is an elevational view of a switch constructed in accordancewith the invention;

FlG. 2 is a vertical sectional view on a greatly enlarged scale of theswitch; and

FIG. 3 is a schematic wiring diagram of a typical circuit with which theswitch may be used.

Apparatus constructed in accordance with the invention comprises a'hollow, cylindrical casing 1 formed of insulating material such as nylonor the like and within which is a concentric, electrically conductivesleeve 2 constituting a contact of a circuit yet to be described. Thesleeve has an axially elongated, diametral, lost motion slot 3 betweenits ends. The upper end of a link 4 extends into the sleeve 2 and isfixed to the latter by means of a pin 5. The lower end of a link 6 alsoextends into the sleeve 2 and is connected to the latter by means of aforce transmitting pin 7 which passes through the slot 3 so as to permitlimited lost motion between the link 6 and the sleeve 2 and between thelinks 4 and 6. The links 4 and 6, together with the pin 7, constituteswitch operating means as will be pointed out hereinafter.

Encircling the sleeve 2 and arranged on opposite sides of the pin 7 is apair of electrically conductive washers 8 and 9. in face to faceengagement with the washer 8 is an annular, pressure sensitive switchingmember 10 and in axially spaced, confronting relation with the member 10is an annular conductor 11 having a pair of axially extending contactlegs 12 which parallel the inner wall of the housing 1. Fitted withinthe legs 12 is a rigid, annular plug 13 formed of insulating materialsuch as nylon and which is fixed with respect to the casing 1 by the pin5 and by an electrically conductive screw 14 which extends through thecasing l and through one leg 12 of the conductor 11 so as to connect tothe latter an electrically conductive wire 15.

in face to face engagement with the conductive washer 9 is a pressuresensitive switching member 16 similar in all respects to the member 10.In axially spaced relation to the switch 16 is an annular conductor 17corresponding to the conductor 11 and from which extends a pair ofcontact legs 18 which parallel the wall of the casing 1. An insulatingplug 19 similar to the plug 13 is accommodated between the legs 18 andis fixed with respect to the casing 1 by a pair of screws 20corresponding to the screw 14. One of the screws 20 connects a wire 21to one of the legs 18 of the conductor 17. A wire 22 is coupled by meansof a conductive clamp 23 to the link 6.

The central opening in each of the annular conductors 11 and 17 islarger than the outside diameter of the sleeve 2, thereby providing anannular space between each of the annular conductors and the sleeve. Theplugs 13 and 19, however, include axially extending, annular projections24 and 25, respectively, which occupy the annular spaces and bearagainst the associated switches 10 and 11. The projections 24 and 25thus perform the function of providing axial spacing between theswitches and their respective conductors 11 and 17, and the projectionsalso provide concentrated force applying means in a manner and for apurpose presently to be described.

Each of the switches 10 and 16 may correspond to one of those disclosedin application Ser. No. 857,941, filed Sept. I5, 1969, and to whichreference may be had for a more detailed disclosure of the manner ofconstructing the switches. Briefly, however, each switch 10 and 16comprises an annular pad of resilient, deformable, non-conductive,synthetic rubber material such as that produced by combining Dow Corningsilicone 3120 with Dow Corning catalyst S or F and throughout which isdispersed a large number of electrically conductive particles such ascommercially available, silver coated, copper particles. The body ofeach switch is completely moisture impervious and may be formed bymixing the silicone resin and catalyst and stirring the conductiveparticles therein, following which the mixture may be cast in a mold andcured. The dispersion, the size and the quantity of particles are suchthat when the body is in its normal, unstressed condition the electricalresistance of the body is infinite and the body is non-conductive. Whenthe body is subjected to compressive force of sufficient magnitude,however, the particles are forced to move relatively to one another intoparticle-to-particle engagement. The resistance of the body changes tothat of the metal particles and the body becomes electricallyconductive. Upon release of the compressive force, the inherentresilience of the body restores it to its normal, unstressed conditionwhereupon the particles again move relatively to one another, but inthis instance in such manner as to disengage one another and render thebody non-conductive. The two pads constituting the switches yieldablymaintain the links 4 and 6 in their normal positions in which neither ofthe switches is conductive.

Only one of the switchesl and 16 may be rendered conductive at one time.If the switch is to be rendered conductive, a compressive force ofsufficient magnitude must be applied to it to establish a conductivepath via the conductive particles between the conductors 8 and 11. Thismay be accomplished by applying a downward force on the link 6 ofsufficient magnitude to take up the lost motion between the pin 7 in theslot 3 in the sleeve 2 and to cause the pin 7 to bear against theconductor 11 so as to compress the pad 10 between the conductor 11 andthe conductor 8. The projection 24 will provide a concentration of forceadjacent the conductor 11 so as to assure establishing a conductive paththrough the switch 10.

To render the switch 16 conductive the pin 7 must be moved upwardly soas to compress the switch 16 between the conductors 9 and 17. Suchmovement of the pin 7 may be accomplished by upward movement of the link6 a distance sufficient to take up the lost motion between the pin 7 andthe sleeve 2 and effect compression of the switch 16 between the parts 9and 17. The projection 25 will provide a high concentration of forceadjacent the conductor 17 so as to assure the establishing of aconductive path through the switch 16.

Although the foregoing description refers to upward and downwardmovements of the link 6 to effect compression of the respective switches16 and 10, it will be understood that the application of a pulling forceon the links 4 and 6 simultaneously, so as to extend the links, willeffect compression of the switch 16, whereas the application of pushingforces on the links 4 and 6 simultaneously, so as to cause retraction ofthe links, will effect compression of the switch 10.

FIG. 3 discloses schematically one arrangement for operating electricmotors by means of switches constructed according to the invention. Asshown, there are four reversible DC. motors M, the armatures of all ofwhich are connected in parallel circuit relation between power lines L-]and L-2. The switch 10 is shown connected between the wires and 22 andconnected to a battery B by the line 22. The switch 16 is shownconnected between the wires 21 and 22 and connected to the battery bythe line 22.

The apparatus includes a double pole, double throw relay 26 having twosimilarly wound windings 27 and 28. One end of each winding is adaptedto be connected to the battery B through the switches 10 and 16,respectively. The opposite ends of the relay windings are joined and areconnected to the emitter of a PNP transistor T having its collectorgrounded. A capacitor 29 is connected between ground and the base of thetransistor T. The junction of the capacitor and the base of thetransistor is connected through resistors 30 and 31 to the lines 15 and21, respectively. The relay 26 has two switching contacts 32 and 33which are adapted to connect the four motors M to the battery B.

When the switch 10 is rendered conductive the relay 27 is energized andeffects movement of the switching contacts 32 and 33 to the left so asto connect the battery B to the armatures of all of the motors M via thelines L-] and L-2. The polarity of the battery should be such as toeffect driving of the motors M in one direction.

When the switch 16 is rendered conductive, the winding 28 is energizedto effect movement of the switching contacts 32 and 33 to the right,thus connecting the armatures of the motor M to the battery B with areverse polarity. The motors thus will be driven in the oppositedirection.

Regardless of which switch is rendered conductive, the emitter of thetransistor T will be connected to the positive side of the battery Bthrough the appropriate winding 27 or 28 so as to bias the transistorforwardly into conduction. Simultaneously, the capacitor 29 will beginto charge and within a very short time, such as one second, the chargeof the capacitor will be sufficient to decrease the forward bias on thebase-emitter junction to render the transistor T non-conductive. Whenthe transistor is rendered non-conductive, the current through thewinding 27 or 28 ceases and the switch contacts 32 and 33 return totheir neutral positions as shown in FIG. 3, whereupon the motors M willbe disconnected from the power source. In essence, therefore, each ofthe motors is energized by a current pulse of short duration.

Although the transistor T is rendered non-conductive shortly afterenergization of the motors M in either direction of operation, thecapacitor 29 will maintain its reverse biasing charge through theresistor 30 or 31 until such time as the actuated switch is renderednonconductive and opens the circuit to the capacitor 29, at which timethe capacitor will discharge through the transistor T. The discharge ofthe capacitor is at a slower rate than its charging rate, however, so asto require two or more seconds before the transistor can be renderedconductive. Thus, the apparatus has a time delay characteristic whichprevents rapid motor reversing operations such as may be attempted by achild and which would be harmful to the apparatus.

The relative sensitivities of the switches 10 and 16 may be varied inany one of several ways. For example, the switch 10 could haveincorporated in it a larger number of conductive particles than areincluded in the switch 16. Alternatively, the switch 10 could be mademuch thinner than the switch 16, thereby requiring less travel of thelinks 4 and 6 toward one another to render the switch 10 conductive.

The disclosed embodiment is representative of the presently preferredform of the invention, but is intended to be illustrative rather thandefinitive thereof.

What is claimed is:

1. A switch construction comprising a pair of normally non-conductiveswitching members each of which is composed of a resilient, compressiblebody of non-conductive, elastomeric material having a plurality ofelectrically conductive, discrete particles dispersed therein, thequantity and size of said particles being such that each of saidswitching members is nonconductive until a sufficient compressive forceis applied thereto to compress said body and effect movement of asufficient number of said particles into engagement to establish throughsaid body an electrically conductive path having a resistancecorresponding substantially to the resistance of the engaged particles;electrically conductive force applying means interposed between saidswitching members in a position to bear against either of said switchingmembers to apply a compressive force thereto; and operating means formoving said electrically conductive force applying 3. The constructionset forth in claim 1 including means associated with said switchingmembers and operable to concentrate the force applied by said forceapplying means to said selected one of said switching members.

4. The construction set forth in claim 1 including a casing in whichsaid switching members are contained in spaced apart relation.

5. The construction set forth in claim 5 wherein said operating meanscomprises a pair of relatively movable links extending into said casingfrom opposite ends of the latter, and a force applying member carried byone of said links and interposed between said switching members.

6. A switch construction for connecting an input circuit line to eitherof a pair of coutput circuit lines comprising a pair of normallynon-conductive switching members each of which is composed of aresilient, compressible body of non-conductive, elastomeric materialhaving a plurality of electrically conductive, discrete particles beingsuch that each of said switching members is nonconductive until asufficient compressive force is applied thereto to compress said bodyand effect movement of a sufficient number of said particles intoengagement to establish through said body an electrically conductivepath having a resistance corresponding substantially to the resistanceof the engaged particles, each one of said switching members beingadapted to be connected to a different one of said output lines;electrically conductive force applying means interposed between saidswitching members in a position to bear against either of said switchingmembers to apply a compressive force thereto; and electrically conductive operating means, adapted to be connected to said input circuitline, for moving said force applying means into and out of forceapplying relation with a selected one of said switching members toconnect said input line to one of said output lines via a path includingsaid operating means and said one of said switching members.

7. The construction set forth in claim 6 wherein at least one of saidswitching members has an opening therein through which said operatingmeans extends.

8. The construction set forth in claim 6 wherein each of said switchingmembers has an opening therein through which said operating meansextends, said operating means comprising a pair oflinks axiallyextensible and retractable relative to said casing.

1. A switch construction comprising a pair of normally nonconductiveswitching members each of which is composed of a resilient, compressiblebody of non-conductive, elastomeric material having a plurality ofelectrically conductive, discrete particles dispersed therein, thequantity and size of said particles being such that each of saidswitching members is nonconductive until a sufficient compressive forceis applied thereto to compress said body and effect movement of asufficient number of said particles into engagement to establish throughsaid body an electrically conductive path having a resistancecorresponding substantially to the resistance of the engaged particles;electrically conductive force applying means interposed between saidswitching members in a position to bear against either of said switchingmembers to apply a compressive force thereto; and operating means formoving said electrically conductive force applying means into and out offorce applying relation with a selected one of either of said switchingmembers to apply a compressive force sufficient to render itelectrically conductive, said operating means being capable of applyingsuch force to one only of said switching members at any one time.
 2. Theconstruction set forth in claim 1 wherein said switching members arearranged in spaced relation and wherein said operating means includes aforce applying member interposed between said switching members.
 3. Theconstruction set forth in claim 1 including means associated with saidswitching members and operable to concentrate the force applied by saidforce applying means to said selected one of said switching members. 4.The construction set forth in claim 1 including a casing in which saidswitching members are contained in spaced apart relation.
 5. Theconstruction set forth in claim 5 wherein said operating means comprisesa pair of relatively movable links extending into said casing fromopposite ends of the latter, and a force applying member carried by oneof said links and interposed between said switching members.
 6. A switchconstruction for connecting an input circuit line to either of a pair ofcoutput circuit lines comprisinG a pair of normally non-conductiveswitching members each of which is composed of a resilient, compressiblebody of non-conductive, elastomeric material having a plurality ofelectrically conductive, discrete particles being such that each of saidswitching members is nonconductive until a sufficient compressive forceis applied thereto to compress said body and effect movement of asufficient number of said particles into engagement to establish throughsaid body an electrically conductive path having a resistancecorresponding substantially to the resistance of the engaged particles,each one of said switching members being adapted to be connected to adifferent one of said output lines; electrically conductive forceapplying means interposed between said switching members in a positionto bear against either of said switching members to apply a compressiveforce thereto; and electrically conductive operating means, adapted tobe connected to said input circuit line, for moving said force applyingmeans into and out of force applying relation with a selected one ofsaid switching members to connect said input line to one of said outputlines via a path including said operating means and said one of saidswitching members.
 7. The construction set forth in claim 6 wherein atleast one of said switching members has an opening therein through whichsaid operating means extends.
 8. The construction set forth in claim 6wherein each of said switching members has an opening therein throughwhich said operating means extends, said operating means comprising apair of links axially extensible and retractable relative to saidcasing.